1. Field of the Invention
The present invention relates generally to collagen and collagen-derived compositions and methods for their preparation. In particular, the present invention relates to a method for producing a dry cross-linked gelatin or other collagen or collagen-derived composition which is capable of absorbing water at an enhanced rate.
Fusion Medical Technologies, Inc., assignee of the present application, produces a hemostatic composition under the FloSeal® trade name. The FloSeal® product is available in a package including two syringes. A first syringe is filled with granules of cross-linked bovine gelatin which are pre-hydrated with a buffer solution. The gelatin hydrogel contains about 85% (w/w) water and is in the form of a flowable hydrogel. Immediately prior to use in the operating room, thrombin in aqueous saline is mixed with the gelatin hydrogel. The thrombin is prepared in saline and drawn up in a second syringe, and the syringes are connected together permitting mixing of thrombin and the gelatin.
The resulting mixture of the gelatin hydrogel granules and the thrombin has been found to be a highly effective hemostatic sealant when applied to a bleeding site. Typically, the sealant will be applied through the syringe in which it has been mixed to the bleeding site. Blood will percolate through the resulting bed of hydrogel granules, and the thrombin reacts with fibrinogen in the blood to form a fibrin clot around the gelatin to seal the bleeding site.
Although highly effective, the present FloSeal® product has a limited shelf life. It is believed that the stability of the gelatin is reduced by hydrolysis of the packaged hydrogel. To limit possible hydrolytic degradation, the FloSeal® product is usually shipped in a temperature-protected packaging.
For these reasons, it would be desirable to provide improved hemostatic sealing compositions of the type which combine a collagen, gelatin, or other collagen-derived hydrogel with a thrombin-containing aqueous solution. In particular, it would be desirable to provide such compositions in a form which would be resistant to hydrolytic degradation and which would therefore have a longer shelf life. It would be particularly desirable to provide improved compositions having both comparable hemostatic activity to the present FloSeal® product and longer shelf lives. Such compositions would be most beneficial if they could be rapidly re-hydrated for subsequent use, typically so that they could be extruded through a syringe. At least some of these objectives will be met by the inventions described hereinafter.
2. Description of the Background Art
The FloSeal® product available from Fusion Medical Technologies, Inc., is described in Hood et al., Efficacy of Topical Hemostat FloSeal™ Vascular Surgery, an Abstract funded by Fusion Medical Technologies, Inc., which was publicly presented in September 1999. Patents covering the FloSeal® product include U.S. Pat. Nos. 6,063,061 and 6,066,325. A dual syringe system suitable for mixing and delivering a collagen, gelatin, or other collagen-derived component and a thrombin component of the FloSeal™ product is described in U.S. Pat. No. 5,908,054. The complete disclosures of each of these patent references is hereby incorporated by reference.